1. Field of the Invention
The invention relates to a regulator insert for valves, such as valves used for controlling liquid flow in a plant for central heating or air conditioning.
2. The Prior Art
Such regulator insert is known from eg WO 95/12082 showing a regulator insert that comprises a housing which is, at the one end, provided with radial inflow openings and, at the one end, provided with radial inflow openings and, at the other end, with radial and axially extending slot-shaped outflow openings. The insert is configured with a roller membrane that closes off the outflow openings to a smaller or larger degree in response to the difference in pressure across the insert, so as to accomplish an essentially constant liquid flow through the insert. The roller membrane is influenced by two oppositely oriented forces; viz, on the side where the outflow openings are located, by the pressure within the insert and a helical spring that seeks to keep the outflow openings open and, on the opposite side, by the pressure prevailing immediately outside the inflow openings of the insert, liquid communication being established there between. In case of a given difference in pressure across the insert, the roller membrane will adapt at a state of equilibrium between these forces which results in a constant liquid flow through the insert. In the shown regulator insert the overall area of the inflow openings can be set incrementally in advance—preferably to a desired constant liquid flow through the insert.
When a regulator insert of this type is mounted in eg a central heating plant, pressure conditions sometimes prevail in the plant that causes the roller membrane in the regulator insert to close off the outflow openings completely, following which it will, however, immediately reopen the outflow openings. Since all the slot-shaped outflow openings have the same axial length, the complete closure occurs very suddenly, which also contributes to quick reopening of the outflow openings. The roller membrane may hereby be caused to oscillate thereby causing undesired pressure conditions in the entire plant. Usually this is only a minor problem, if only one or a few regulator inserts of this type is/are used. Often, however, large numbers of regulator inserts are used that may, in adverse conditions, initiate each other to oscillate simultaneously and whereby so comprehensive oscillation problems may occur throughout the plant that it is destroyed.
It is the object of the invention to provide a regulator insert of the type mentioned above, wherein said problem cannot occur.